| 2023 Hardiness Zone: | Zone 5a: -20°F to -15°F Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5a: -20°F to -15°F |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 53b - Kettle Moraines |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 53029 - Hartland, WI | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 8 | 13 | 24 | 35 | 47 | 56 | 61 | 59 | 50 | 39 | 27 | 15 | 36 |
| Avg Max Temp (°F) | 25 | 30 | 42 | 55 | 68 | 78 | 82 | 79 | 71 | 59 | 43 | 30 | 55 |
| Avg Precip (In.) | 1.36 | 1.2 | 2.09 | 3.32 | 3.07 | 3.85 | 3.97 | 4.38 | 3.54 | 2.56 | 2.43 | 1.73 | 33.51 |